MHC I mediated presentation of peptides derived from many glycoproteins requires translocation from the endoplasmic reticulum (ER), following synthesis, to cytosolic proteasomes for degradation. Immune mediated clearance of, and recovery from, hepatitis B virus (HBV) is thought to involve recognition of MHC I presented HBV glycoproteins by T lymphocytes. Failure to resolve HBV infection resulting in chronic disease is associated with an inadequate MHC I restricted lymphocyte response. This proposal will determine if the MHC I presentation of HBV envelope glycoproteins can be enhanced by production of variants that are degraded with enhanced efficiency by cytosolic proteasomes. Briefly, plasmids specifying mutant envelope proteins unable to enter the ER, and misfold, will be constructed and tested for enhanced degradation and MHC I presentation to human and woodchuck CTLs, in tissue culture. Promising constructs will then be introduced into naive and, if indicated, hepadnavirus chronically infected woodchucks and tested for MHC I presentation. The effect of delivery of plasmids into infected versus uninfected cells upon clearance of virus will be compared. This work will thus help in our understanding of the role proteasome degradation in MHC I presentation of HBV, as well as test the possibility that manipulation of the immune system by expression of mutant polypeptides is beneficial.